This invention relates to tool components and more particularly to tool components which utilise abrasive compacts as the cutting edge or surface.
Abrasive compacts are well known in the art and are used extensively in industry for the abrading of various workpieces. They consist essentially of a mass of abrasive particles present in an amount of at least 70 percent, preferably 80 to 90 percent, by volume of the compact bonded into a hard conglomerate. Compacts are polycrystalline masses and can replace single large crystals. The abrasive particles of compacts are invariably ultra-hard abrasives such as diamond and cubic boron nitride.
Abrasive compacts generally contain a second phase or bonding matrix which contains a catalyst (also known as a solvent) useful in synthesising the particles. In the case of cubic boron nitride, examples of suitable catalysts are aluminium or an alloy of aluminium with nickel, cobalt, iron, manganese or chromium. In the case of diamond, examples of suitable catalysts are metals of Group VIII of the Periodic Table such as cobalt, nickel or iron or an alloy containing such a metal. Diamond and cubic boron nitride compacts are manufactured under conditions of temperature and pressure at which the abrasive particle is crystallographically stable. Consequently, compacts include a considerable amount of direct particle-to-particle bonding.
Abrasive compacts may be bound directly to a tool or shank for use. Alternatively, they may be bonded to a backing such as a cemented carbide backing prior to being mounted on a tool or shank. Abrasive compacts bonded to cemented carbide support backings are known in the art as composite abrasive compacts. Bonding of the abrasive compact to the support backing may be achieved directly or through a metal bonding layer. Examples of patent specifications describing abrasive compacts, composite abrasive compacts and their manufacture are U.S. Pat. Nos. 3,743,489, 3,767,371, 4,063,909 and 3,745,623.
Cutting components for drill bits and utilising composite abrasive compacts have been described in the literature and have been used commercially. Such cutting components comprise an elongate pin of cemented carbide to which is bonded a composite abrasive compact, bonding being achieved through the carbide support of the composite abrasive compact. Bonding between the carbide support and the elongate pin is achieved by a braze metal which has a melting point above 700.degree. C. Such a high temperature braze, so the art teaches, is essential in order to achieve a sufficiently strong bond between the composite abrasive compact and the elongate pin. Reference in this regard may be had to the disclosures of U.S. Pat. No. 4,225,322.
It has recently been proposed to use abrasive compacts and composite abrasive compacts as tool inserts for mining machines of the kind which are used to cut a variety of soft materials such as coal. In mining machines of this type, a plurality of cutting tools (also known as picks) are positioned on a working surface, for example, on the surface of a drum, and moved in a cutting direction against the face of the material to be cut. Each tool comprises a holding lug and an insert usually secured in a bore or socket in the lug. The cutting edge or surface of the insert is made of a wear-resistant material such as cemented carbide or abrasive compact.